The present invention relates to a method of electroplating a Nixe2x80x94Fexe2x80x94P alloy using a sulfamate solution and, in particular, to a method of elecrtro-plating a Nixe2x80x94Fexe2x80x94P alloy using a plating solution containing nickel sulfamate, iron sulfamate, phosphorous acid, and a buffer agent.
As well known to those skilled in the art, when the microstructure of a material is controlled at the nano-scale, desirable physical properties such as excellent ductility and hardness can be easily secured. So researches on nano-technologies are active in the material field. In particular, many efforts to use the nano-technology in the automobile and aviation industries have been made to develop nanoparticle reinforced light materials, nanoparticle reinforced tires, coating materials not requiring a washing process, fire resistant plastics, electronic control devices, self-healing coatings and fibers and so on. At this time, an electroplating is used in economically producing the nano materials.
Meanwhile, Inconel alloy or stainless steel used as material of steam generator tubes in nuclear power plants fails due to stress corrosion cracking as the operating time increases time, thus requiring frequent repairing. In particular, it is very important to properly repair the failed the steam generator tubes to prevent the leakage of primary cooling water contaminated with radioactive materials in nuclear power plants. The failed steam generator tubes have been repaired using an conventional alloy welding or a laser beam welding processes. However, these processes are induce high thermal residual stress in the parent metal and weld. If the repairing is accomplished by an electroplating process, such problems due to the residual thermal stress can be avoided, thereby desirable repairing the failed steam generator tubes. Accordingly, active researches for electroplating stainless steel or Ni-based Inconel alloys are currently pursued.
The electroplating Nixe2x80x94P and Nixe2x80x94Fe alloys among various Ni-based alloys has been highlighted because of their excellent mechanical properties and corrosion resistance and a possibility of being used to produce an excellent magnetic alloy thin film. However, the Nixe2x80x94P alloy has the disadvantage of poor mechanical properties owing to the rapid grain growth at a temperature of 350xc2x0 C. or higher, and the Nixe2x80x94Fe alloy is disadvantageous in that a content of Fe in the Nixe2x80x94Fe alloy is not easily controlled.
In addition, researches on electroplating the Nixe2x80x94Fexe2x80x94P alloy, a ternary alloy of Nixe2x80x94P and Nixe2x80x94Fe alloys, has not been done so actively mainly due to complexity and difficulty in controlling the composition of the Nixe2x80x94Fexe2x80x94P alloy. Recently, however, the Nixe2x80x94Fexe2x80x94P alloy is highlighted because corrosion and thermal resistance are readily improved by desirably controlling Fe content in the Nixe2x80x94Fexe2x80x94P alloy, unlike the Nixe2x80x94P alloy, and the Fe content in the Nixe2x80x94Fexe2x80x94P alloy is easily controlled by adding P to the Nixe2x80x94Fe alloy, unlike the Nixe2x80x94Fe alloy.
Japanese Pat. No. 5190725 discloses a method of electroplating Nixe2x80x94Fexe2x80x94P alloy using a sulfate (NiSO4) solution so as to improve oxidation resistance, and bending property of a semiconductor element and a wire bonding part. Furthermore, Sridharan and Sheppard, and Pushpavanam and Vaijayanthy suggest a method of plating a Nixe2x80x94Fexe2x80x94P alloy by a sulfate solution [J. Applied Electrochemistry, vol. 29, 1997, p.1198-1206; Bulletin of Electrochemistry, vol. 15, no. 5-6, 1999, p.211-214]. However, these methods are disadvantageous in that an electrodeposition stress is high and a plating rate low, thus being poor in economic efficiency. Accordingly, there remains a need to develop an electroplating method having low electrodeposition stress, and excellent thermal resistance, abrasion resistance, and corrosion resistance, and capable of being quickly plated.
The present inventors have conducted extensive studies on the method of electroplating a Nixe2x80x94Fexe2x80x94P ternary alloy using a sulfamate solution, resulting in the finding that a electrodeposited layer obtained using the method of the present invention has a very low electrodeposition stress and a plating process is very quickly conducted, thereby securing excellent economic efficiency.
Accordingly, the present invention has been made keeping in mind the above disadvantages occurring in the prior art, and an object of the present invention is to provide a method of electroplating a Nixe2x80x94Fexe2x80x94P alloy using a sulfamate solution.